JPS608524B2 - magnetic recording and reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing apparatus using a magnetic tape having tracks for recording and reproducing audio signals and control signals, such as a video tape recorder (VTR). This is intended to improve the sound quality of the audio signal, particularly to reduce wow and flutter.

The recording density on the magnetic tape in recent VTRs has been increasing, and the running speed of the magnetic tape has tended to become slower.

Although this has the advantage that the amount of tape consumed per unit time is small, it has the disadvantage that the quality of the reproduced audio signal deteriorates in terms of frequency characteristics, signal-to-noise ratio, and flutter. Among these, wow-flop ivy causes fluctuations in the sound, cloudiness, etc., and has become a major hindrance, especially when recording and playing back music. Possible ways to reduce the wow and flash of audio signals in a VTR are to mechanically improve the tape running system or to improve the speed control system of the tape drive motor. In the latter case, only extremely low frequency components are improved, so it is very difficult to reduce t wow and flutter.

In order to improve the audio signal quality of a VTR, the present invention utilizes a control track originally included in the VTR, detects tape speed fluctuations based on a reference signal recorded and played back on the control track, and adjusts the audio signal accordingly. This technique attempts to reduce flutter caused by tape speed fluctuations by controlling the delay time.

The present invention will be explained below based on the illustrated embodiments.

FIG. 1 is a block diagram showing the main part of an embodiment of the present invention, and this is an example in which the audio signal wow and flutter of a tape speed control type VTR is reduced. In FIG. 1, during recording, a capstan motor 12 is driven by a reference signal from a reference oscillator 1, but this system is not shown for convenience of explanation. During recording, an audio signal is applied to the audio input terminal 5, passes through a recording amplifier 6, is superimposed with a bias signal generated by a bias oscillator 7, and is supplied to an audio head 8, where it is sent to the audio signal track on the magnetic tape 4. be recorded.

On the other hand, a control reference signal generated by a reference oscillator 1 is applied to a control head 3 via a recording amplifier 2, and is recorded on a control track on a magnetic tape 4.

The video signal is recorded on a video track on the magnetic tape 4 by means of a video head attached to a rotating drum, but this is not shown because it is not directly related to the present invention. In FIG. 1, during reproduction, a control signal is reproduced by a control head 3', amplified by a regenerative amplifier 9, and applied to a phase comparator 10'.

A reference signal from the reference oscillator 1 recorded as a control signal during recording is also applied to the phase comparator 10, and the phase is compared with the reproduced control signal. Therefore, the output of the phase comparator 10 is a voltage corresponding to the fluctuation in the running speed of the magnetic tape 4 during recording and reproduction.
From the output of the phase comparator 10 corresponding to the amount of tape speed variation, only the low frequency component that can be controlled by the motor is extracted by a low-pass filter 11, and the capstan motor 12
is supplied to control the tape running speed during playback. In other words, it constitutes a so-called capstan servo system that operates to maintain the same tape running speed during recording and during playback. Note that the reference signal from the reference oscillator 1 is also given to the rotary head swivel control section 30 as a slit control signal for the video head.

The capstan servo system described above controls the tape speed during recording and playback to be the same, but the frequency of the signal transmitted to the servo system is extremely low due to the control frequency characteristics of the low-pass filter 11 and motor. The frequency component is, for example, IHz or lower. Therefore, tape speed fluctuation components of several Hz to several tens of Hz or more cannot be removed, and when audio signals are reproduced, wow and flutter of several Hz to several tens of Hz2 occurs, degrading the sound quality. That is, tape speed control using the capstan servo alone could not sufficiently remove wow and flutter from the audio signal. This is the point of this invention! Taking this into consideration, by adding a voltage controlled oscillator 14 and a variable delay circuit 15 as shown in FIG. 1, the wow and flutter of the audio signal can be removed. This point will be explained in detail below. The reproduced signal obtained at the audio head 8' is frequency-equalized by an equalizing amplifier 13, passed through a variable delay circuit 15, further amplified by a line amplifier 16, and guided to an audio output terminal 17. As mentioned above, phase comparator 1
At 0, an output voltage corresponding to the difference in tape speed between recording and reproduction, that is, the amount of variation in tape speed is obtained.

This world voltage controls the repetition frequency of the pulses generated by the voltage controlled oscillator 14. Therefore, the repetition frequency of the pulses generated by the voltage controlled oscillator 14 changes in accordance with the amount of variation in the running speed of the magnetic tape 4. The variable delay circuit 15 is, for example, a bucket brigade device (
It includes a charge transfer element such as a charge coupled device (BBD) or a charge coupled device (CCD), and its delay time is controlled by the repetition frequency of the applied clock pulse. Therefore, if the variable delay circuit 15 is driven using the pulse generated by the voltage controlled oscillator 14 as a clock pulse, a delay time corresponding to the amount of variation in tape speed can be obtained. Now, let us consider a case where wow and flutter occurs in the direction in which the tape speed during reproduction of the magnetic tape 4 increases and the frequency of the reproduced audio signal increases.

In this case, the output voltage of the phase comparator 10 is set to be 4.0 times lower than when the tape speed fluctuation is zero, so that the repetition frequency of the pulses generated by the voltage controlled oscillator 14 is low. As a result, the delay time caused by the variable delay circuit 15 becomes longer. On the other hand, if the tape speed during playback slows down and the frequency of the playback audio signal is affected by wow and flutter, the delay time of the variable delay circuit is controlled to be short. As described above, the wow and flutter of the audio signal caused by tape speed fluctuations is reduced by passing through the variable delay circuit 15, and an audio signal with reduced wow and flutter is obtained at the audio output terminal 17. In this case, the frequency component of the wow and flutter to be reduced is several HZ because the oscillation frequency of the reference oscillator 1 is 30Hz.
Although the frequency component is below Z, it has a very large improvement effect considering that the frequency component that is easiest to detect in terms of wow and flutter is 2 to 4 Hz. Here, variable delay circuit 1
For example, if a BBD is used for 5, the required number of stages is, assuming that the minimum fluctuation frequency of wow and flutter is IHZ and the maximum frequency fluctuation amount is 1%, the maximum time fluctuation amount is 1.6 m.
sec, and if the clock frequency is set to 50 KHz considering the audio signal bandwidth, the number of stages becomes approximately 160, which is a sufficiently practical number of stages. FIG. 2 is a block diagram of a main part of another embodiment of the present invention, and is an example of application to a VTR without tape speed control.

Note that blocks having the same functions as those in the embodiment shown in FIG. 1 are given the same reference numerals. During recording, the audio signal is recorded on the audio track on the magnetic tape 4 in exactly the same manner as in FIG. On the other hand, a vertical synchronization separator 19 separates a vertical synchronization signal from the video signal applied to the video input terminal 18 for the control track.
A control signal of about 30 Hz is recorded by the control head 3. During reproduction, the control signal reproduced by the control head 3' and the regenerative amplifier 9 is applied to the phase comparator 10 and coupled to the flywheel oscillator 21, which generates a frequency that averages out the frequency fluctuations of the reproduced control signal. .

That is, the output of the flywheel oscillator 21 is the average value of the frequency fluctuations of the reproduction control signal caused by tape speed fluctuations, which are added to the phase comparator 10'. Therefore, the output of the phase comparator 10 provides a voltage corresponding to the amount of speed fluctuation at each instant with respect to the average value of the tape running speed. This voltage is applied to the voltage controlled oscillator 14 to control the repetition frequency of the generated pulses and change the delay time of the variable delay circuit 15 in the audio signal path, thereby reducing the wow and flutter of the audio signal as shown in FIG. This is similar to the example. In short, the embodiment of FIG. 2 does not have a reference oscillator, and therefore differs from FIG. 1 in that a reference signal is generated from the reproduction control signal and the flywheel oscillator 211. Note that the switching control signal for the rotary head may be provided by the output of the regenerative amplifier 9. FIG. 3 is a block diagram of a main part of still another embodiment of the present invention, and like the embodiment of FIG. 1, this is an example of application to a tape speed control type VTR. The difference from the embodiment shown in FIG. 1 is that the frequency of the control signal recorded on the control track is increased. Therefore, the oscillation frequency of the reference oscillator 22 is
It is n times the 30Hz used in . Head switching control is performed by converting the output of the reference oscillator 22 into a 1/n frequency divider 23.
This is performed using a signal frequency-divided to 1/n frequency, that is, 30Hz. A control signal regenerated by the control head 3' and the regenerative amplifier 9 and the oscillation output of the reference oscillator 22 are applied to the phase comparator 10', and the phases are compared. As a result, a voltage corresponding to the amount of variation in tape running speed is obtained at the output of the phase comparator 10. This hot spring,
The frequency of the signal applied to the phase comparator 101 is 30Hz.
Therefore, it is possible to detect tape speed fluctuations with high fluctuation frequencies. That is, in the embodiment shown in FIG. 1, it was not possible to detect fluctuation components of more than 10 days Z, whereas in the embodiment shown in FIG. can be detected.
The output voltage corresponding to the tape speed variation obtained by the phase comparator 10 is used to control the capstan motor, and also changes the oscillation frequency of the voltage controlled oscillator Turtle, thereby changing the delay time of the variable delay circuit Turtle 5. Controlling the wow and flutter of the audio signal to reduce the wow and flutter of the audio signal is similar to the embodiment shown in FIG. According to this embodiment, flutter, which is a relatively high frequency component, can be easily removed, so that the reproduced audio signal is of good quality without any cloudiness. FIG. 7 is a configuration diagram of main parts of another embodiment.

Similar to the embodiment shown in FIG. 3, this embodiment is designed to effectively remove flutter, which is a high frequency component. A high frequency pilot signal is used to detect speed fluctuations. In other words, recording on the control track is performed by mixing the approximately 30Hz oscillation output of the L reference oscillator 1 with the output of the pilot signal generator 27 that generates an arbitrary frequency higher than that in the mixer 24, and then using the recording amplifier 2 and The control head 3 records the signal as a control signal. That is, 30Hz used in the VTR control system and a pilot signal for reducing wow and flash are recorded by frequency multiplexing. The reproduction temple says, ``The control head 3' and the reproduction amplifier 9 reproduce the frequency multiplexed signal,'' and the signal separator 25 converts it to the VTR.
It is separated into a 30Hz signal for the control system and a pilot signal for wow and flutter reduction. The signal separator 25 can be easily constructed by, for example, a low frequency wave generator and a high frequency wave generator. separated 3
The 0HZ signal is used to control the capstan motor and the head sliding door in exactly the same way as in the embodiment shown in FIG. on the other hand,
The regenerated pilot signal is sent to the pilot signal generator 2.
7 is applied to the phase comparator 26, and the phases of the two are compared to obtain a voltage corresponding to the amount of tape speed variation.

In this case, if the generation frequency of the pilot signal generator 27 is selected to be, for example, IKHz, it is possible to detect wow and flutter up to several hundred Hz, which is converted into an audio signal by the voltage controlled oscillator 14 and the variable delay circuit 15. The resulting wow and flutter can be removed up to very high frequency components. As described in detail above, the present invention detects the amount of tape speed fluctuation by comparing the phase of the control signal recorded and played back on the control track of the VTR with the reference signal, and reproduces from the audio track according to the amount of fluctuation. Since the delay time given to the reproduced audio signal is controlled, wow and flutter in the reproduced audio signal of the VTR can be effectively reduced.

As a result, it is possible to eliminate one of the major obstacles to the sound quality of recording and playback using magnetic tape, and it is possible to obtain high-quality playback sound without muddying or wobbling. slow small V
It will be extremely effective if used for TR, etc. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of the main parts of an embodiment of the present invention, FIG.
FIG. 3 and FIG. 4 are respective configuration diagrams of main parts of other embodiments of the present invention.

1...Reference oscillator ~ 3, 3'...

Control head, 4...magnetic tape ~ 5...audio input terminal, 6...recording amplifier, 7...bias oscillator, 8, 8'...audio head, 10...phase comparator, turtle 3 ... Equalization amplifier, 14 ... Voltage controlled oscillator,
Tortoise 5...Variable delay circuit, 16...Line amplifier, 1
7... Audio output terminal, 19... Vertical sync separator, 2
0...・1/2 frequency divider, 21...B flywheel oscillator, 22...Reference oscillator, 23...1/n frequency divider, 24...Mixer, 25... Signal separator, 26... Phase comparator, 27...'pilot signal generator. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. A magnetic recording and reproducing device using a magnetic tape having a control track and an audio track as well as a video track, in which a reference signal for controlling the position of the video head is applied to the control track during recording, and a reference signal is applied to the audio track for controlling the position of the video head. The audio signal is recorded, and during playback, the position of the video head is controlled by the signal played back from the control track, the tape speed fluctuation component is detected, and the delay time of the variable delay circuit placed in the audio signal playback path is adjusted as above. A magnetic recording and reproducing device characterized in that wow and flutter in a reproduced audio signal can be reduced by controlling according to a speed fluctuation component. 2. In the description of claim 1, a reference oscillator is provided, and the detection of the tape speed fluctuation component is performed by comparing the phase of the signal reproduced from the control track and the reference signal of the reference oscillator used during recording. 1. A magnetic recording and reproducing device characterized in that it is configured to perform the following operations. 3. In the statement of claim 1, the vertical synchronization signal of the video signal is used as a reference signal, and the detection of the tape speed fluctuation component is performed using a signal reproduced from a control track and a flywheel driven with reference to the signal. A magnetic recording/reproducing device characterized in that the magnetic recording/reproducing device is configured to perform phase comparison with a signal from an oscillator. 4. In the statement of claim 1, 2, or 3, the variable delay circuit is configured with a charge transfer element,
A magnetic recording/reproducing apparatus characterized in that a voltage controlled oscillator is driven by a voltage obtained by phase comparison as the tape speed fluctuation component, and the oscillation output is used as a clock pulse to control the charge transfer element. 5. In the statement of claim 1, the control track records a frequency that is an integral multiple of the control signal frequency recorded by a normal video tape recorder as a reference signal, and the tape is recorded from the signal reproduced by the control track. A magnetic recording/reproducing apparatus characterized in that a speed fluctuation component is detected and the reproduction signal is frequency-divided to be used as a control signal for a video tape recorder. 6. In the description of claim 1, a control signal recorded by a normal video tape recorder and a pilot signal having a higher frequency than the control signal are multiplex recorded on the control track, and the control signal and the control signal are multiplexed during playback. 1. A magnetic recording and reproducing device characterized in that a pilot signal is separated and used for controlling a video tape recorder and reducing wow and flutter of an audio signal.